For La traversée des Monts Sutton, I carried 4 gels and 3 bars and 1L of water. I knew there would be streams with drinkable water along the trails, so I've managed to refill my bottles 2 times using purification tablets.
The trails were really dry, making the run enjoyable. Although, I was surprised of how technical the trails where. With the steepness, it got really hard to be consistent and maintain a good pace.